Mark 8:5

‘And he asked, “How many loaves have you?” And they said, “Seven”.'

Jesus knew His disciples had some food and asked what loaves they had. The reply was ‘seven'. At this the ears of everyone who was listening to the Gospel being read, and believed in Jesus, would prick up. Every listener would recognise the divinely perfect number, conveying the idea that there was sufficient there for God to do what He would if only the disciples realised it. This was why Mark added the mention of fish only as a secondary item. He did not want to take away from the impact of ‘seven loaves'.